Method to trigger in-device coexistence interference mitigation in mobile cellular systems

ABSTRACT

A method to trigger in-device coexistence (IDC) interference mitigation is provided. A wireless device comprises a first radio module and a co-located second radio module. The first radio module measures a received radio signal based on a plurality of sampling instances. A control entity obtains Tx/Rx activity of the second radio module and informs Tx/Rx timing information to the first radio module. The first radio module determines a measurement result based on the obtained timing information. The first radio module triggers an IDC interference mitigation mechanism if the measurement result satisfies a configurable condition. In one embodiment, the first radio module reports IDC interference information and traffic pattern information of the second radio module to a base station for network-assisted coexistence interference mitigation. The IDC triggering mechanism prevents unnecessary and arbitrary IDC request from the device and thus improves network efficiency.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 from U.S.Provisional Application No. 61/373,142, entitled “Method to TriggerIn-Device Coexistence Interference Mitigation in Mobile CellularSystems,” filed on Aug. 12, 2010; U.S. Provisional Application No.61/373,151, entitled “Method of In-Device Interference Mitigation forCellular, Bluetooth, WiFi and Satellite Systems Coexistence,” filed onAug. 12, 2010; U.S. Provisional Application No. 61/374,046, entitled“Method of In-Device Interference Mitigation for Wireless Systems,”filed on Aug. 16, 2010; U.S. Provisional Application No. 61/374,052,entitled “Method of In-Device Interference Avoidance for wirelessSystems,” filed on Aug. 16, 2010, the subject matter of which isincorporated herein by reference.

TECHNICAL FIELD

The disclosed embodiments relate generally to wireless networkcommunications, and, more particularly, to method of triggeringin-device coexistence interference mitigation.

BACKGROUND

Ubiquitous network access has been almost realized today. From networkinfrastructure point of view, different networks belong to differentlayers (e.g., distribution layer, cellular layer, hot spot layer,personal network layer, and fixed/wired layer) that provide differentlevels of coverage and connectivity to users. Because the coverage of aspecific network may not be available everywhere, and because differentnetworks may be optimized for different services, it is thus desirablethat user devices support multiple radio access networks on the samedevice platform. As the demand for wireless communication continues toincrease, wireless communication devices such as cellular telephones,personal digital assistants (PDAs), smart handheld devices, laptopcomputers, tablet computers, etc., are increasingly being equipped withmultiple radio transceivers. A multiple radio terminal (MRT) maysimultaneously include a Long-Term Evolution (LTE) or LTE-Advanced(LTE-A) radio, a Wireless Local Area Network (WLAN, e.g., WiFi) accessradio, a Bluetooth (BT) radio, and a Global Navigation Satellite System(GNSS) radio.

Due to spectrum regulation, different technologies may operate inoverlapping or adjacent radio spectrums. For example, LTE/LTE-A TDD modeoften operates at 2.3-2.4 GHz, WiFi often operates at 2.400-2.483.5 GHz,and BT often operates at 2.402-2.480 GHz. Simultaneous operation ofmultiple radios co-located on the same physical device, therefore, cansuffer significant degradation including significant coexistenceinterference between them because of the overlapping or adjacent radiospectrums. Due to physical proximity and radio power leakage, when thetransmission of data for a first radio transceiver overlaps with thereception of data for a second radio transceiver in time domain, thesecond radio transceiver reception can suffer due to interference fromthe first radio transceiver transmission. Likewise, data transmission ofthe second radio transceiver can interfere with data reception of thefirst radio transceiver.

FIG. 1 (Prior Art) is a diagram that illustrates interference between anLTE transceiver and a co-located WiFi/BT transceiver and GNSS receiver.In the example of FIG. 1, user equipment (UE) 10 is an MRT comprising anLTE transceiver 11, a GNSS receiver 12, and a BT/WiFi transceiver 13co-located on the same device platform. LTE transceiver 11 comprises anLTE baseband module and an LTE RF module coupled to an antenna #1. GNSSreceiver 12 comprises a GNSS baseband module and a GNSS RF modulecoupled to antenna #2. BT/WiFi transceiver 13 comprises a BT/WiFibaseband module and a BT/WiFi RF module coupled to antenna #3. When LTEtransceiver 11 transmits radio signals, both GNSS receiver 12 andBT/WiFi transceiver 13 may suffer coexistence interference from LTE.Similarly, when BT/WiFi transceiver 13 transmits radio signals, bothGNSS receiver 12 and LTE transceiver 11 may suffer coexistenceinterference from BT/WiFi. How UE10 can simultaneously communicate withmultiple networks through different transceivers and avoid/reducecoexistence interference is a challenging problem.

FIG. 2 (Prior Art) is a diagram that illustrates the signal power ofradio signals from two co-located RF transceivers. In the example ofFIG. 2, transceiver A and transceiver B are co-located in the samedevice platform (i.e., in-device). The transmit (TX) signal bytransceiver A (e.g., WiFi TX in ISM CH1) is very close to the receive(RX) signal (e.g., LTE RX in Band 40) for transceiver B in frequencydomain. The out of band (OOB) emission and spurious emission resulted byimperfect TX filter and RF design of transceiver A may be unacceptableto transceiver B. For example, the TX signal power level by transceiverA may be still higher (e.g. 60 dB higher before filtering) than RXsignal power level for transceiver B even after the filtering (e.g.,after 50 dB suppression).

In addition to imperfect TX filter and RF design, imperfect RX filterand RF design may also cause unacceptable in-device coexistenceinterference. For example, some RF components may be saturated due totransmit power from another in-device transceiver but cannot becompletely filtered out, which results in low noise amplifier (LNA)saturation and cause analog to digital converter (ADC) to workincorrectly. Such problem actually exists regardless of how much thefrequency separation between the TX channel and the RX channel is. Thisis because certain level of TX power (e.g., from a harmonic TX signal)may be coupled into the RX RF frontend and saturate its LNA. If thereceiver design does not consider such coexistence interference, the LNAmay not be adapted at all and keep saturated until the coexistenceinterference be removed (e.g. by turning off the interference source).

Various in-device coexistence (IDC) interference mitigation solutionshave been proposed. For example, an UE may request network assistance tomitigate IDC interference via frequency division multiplexing (FDM),time division multiplexing (TDM), and/or power management principles.However, network resources will be substantially consumed if many UEsrequest network assistance on IDC interference mitigation. Moreover,network efficiency will be degraded if all UEs request IDC assistance.Additional solutions are sought to reduce overhead and to improveefficiency for IDC interference mitigation.

SUMMARY

A method to trigger in-device coexistence (IDC) interference mitigationis provided. A wireless device comprises a first radio module and aco-located second radio module. The first radio module measures areceived radio signal strength or quality based on a plurality ofsampling instances. A control entity within the device obtains Tx/Rxactivity of the second radio module and informs Tx/Rx timing informationto the first radio module. The first radio module determines ameasurement result based on the obtained timing information. The firstradio module triggers an IDC interference mitigation mechanism if themeasurement result satisfies a configurable condition. The IDCtriggering mechanism prevents unnecessary and arbitrary IDC request fromthe device and thus improves network efficiency.

In one embodiment, the first radio module is an LTE/WiMAX radio, and thesecond radio module is a WiFi/BT radio. In one example, the IDCinterference mitigation mechanism is to deactivate the WiFi/BT radiowhen the LTE/WiMAX radio is receiving desired radio signals, or viceversa. In another example, the LTE/WiMAX radio reports IDC interferenceinformation and traffic pattern information of the WiFi/BT radio moduleto a base station for network-assisted coexistence interferencemitigation. The base station then applies various FDM or TDM solutionsaccordingly to mitigate interference. The condition (e.g., a thresholdvalue) for triggering IDC interference mitigation is configurable by thebase station. The base station may configure different thresholds fordifferent scenarios. Moreover, different conditions may be applied totrigger different IDC interference mitigation mechanisms under differentscenarios.

Other embodiments and advantages are described in the detaileddescription below. This summary does not purport to define theinvention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components,illustrate embodiments of the invention.

FIG. 1 (Prior Art) is a diagram that illustrates interference between anLTE transceiver and a co-located WiFi/BT transceiver and GNSS receiver.

FIG. 2 (Prior Art) is a diagram that illustrates the signal power ofradio signals from two co-located RF transceivers in a same deviceplatform.

FIG. 3 illustrates a user equipment having multiple radio transceiversin a wireless communication system in accordance with one novel aspect.

FIG. 4 illustrates a global spectrum allocation around 2.4 GHz ISM bandin more detail.

FIG. 5 illustrates one example of FDM solution for IDC interferenceavoidance.

FIG. 6 illustrates one example of TDM solution for IDC interferenceavoidance.

FIG. 7 illustrates a method of triggering IDC interference mitigationsolution in accordance with one novel aspect.

FIG. 8 is a simplified block diagram of an LTE user equipment having acentral control entity.

FIG. 9 illustrates one embodiment of triggering IDC interferencemitigation.

FIG. 10 illustrates another embodiment of triggering IDC interferencemitigation.

FIG. 11 illustrates an example of IDC interference measurement inaccordance with one novel aspect.

FIG. 12 illustrates an example of reporting traffic and schedulinginformation in accordance with one novel aspect.

FIG. 13 is a flow chart of a method of triggering IDC interferencemitigation.

FIG. 14 is a flow chart of a method of reporting traffic and schedulinginformation for IDC interference mitigation.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings.

FIG. 3 illustrates a user equipment UE31 having multiple radiotransceivers in a wireless communication system 30 in accordance withone novel aspect. Wireless communication system 30 comprises a userequipment UE31, a serving base station (e.g., evolved node-B) eNB32, aWiFi access point WiFi AP33, a Bluetooth device BT34, and a globalpositioning system satellite device GPS35. Wireless communication system30 provides various network access services for UE31 via different radioaccess technologies. For example, eNB32 provides OFDMA-based cellularradio network (e.g., a 3GPP Long-Term Evolution (LTE) or LTE-Advanced(LTE-A) system) access, WiFi AP33 provides local coverage in WirelessLocal Area Network (WLAN) access, BT34 provides short-range personalnetwork communication, and GPS35 provides global access as part of aGlobal Navigation Satellite System (GNSS). To access various radionetworks, UE31 is a multi-radio terminal (MRT) that is equipped withmultiple radios coexisted/co-located in the same device platform (i.e.,in-device).

Due to spectrum regulation, different radio access technologies mayoperate in overlapping or adjacent radio spectrums. As illustrated inFIG. 3, UE31 communicates radio signal 36 with eNB32, radio signal 37with WiFi AP33, radio signal 38 with BT34, and receives radio signal 39from GPS35. Radio signal 36 belongs to 3GPP Band 40, radio signal 37belongs to one of the WiFi channels, and radio signal 38 belongs to oneof the seventy-nine Bluetooth channels. The frequencies of all thoseradio signals fall within a range from 2.3 GHz to 2.5 GHz, which mayresult in significant in-device coexistence (IDC) interference to eachother. The problem is more severe around the 2.4 GHz ISM (TheIndustrial, Scientific and Medical) radio frequency band. In one novelaspect, UE31 triggers IDC interference mitigation mechanism based onaccurate and effective IDC interference measurement result.

FIG. 4 illustrates a global spectrum allocation around the 2.4 GHz ISMband in more detail and the corresponding coexistence interferenceimpact from WiFi to LTE in 3GPP Band 40. As illustrated by the top table41 of FIG. 4, the 2.4 GHz ISM band (e.g., ranges from 2400-2483.5 MHz)is used by both fourteen WiFi channels and seventy-nine Bluetoothchannels. The WiFi channel usage depends on WiFi AP decision, whileBluetooth utilizes frequency hopping across the ISM band. In addition tothe crowded ISM band, WiMAX 1B or 3GPP Band 40 ranges from 2300-2400MHz, and WiMAX 3A or 3GPP Band 7 UL ranges from 2500-2570 MHz, both arevery close to the 2.4 GHz ISM radio frequency band. As a result, withoutadditional interference avoidance mechanism, traditional filteringsolution is insufficient to mitigate IDC interference such thatdifferent radio access technologies can work well independently on thesame device platform. Different solutions have been sought to avoid thecoexistence interference.

FIG. 5 illustrates one example of frequency division multiplexing (FDM)solution for IDC interference avoidance in wireless network 50. Wirelessnetwork 50 comprises a plurality of eNBs and a plurality of UEs. Forcellular network access, the UEs are served by their serving eNBs viadifferent frequency channels (e.g., CH#1-CH#3) in 3GPP Band 40. The UEsare also equipped with in-device WiFi transceivers for WLAN access or BTtransceivers for personal network communication (not shown). When an UEexperiences IDC interference, it is likely for the UE to requesthandover from CH#3 (e.g., closer to the ISM band) to CH#1 (e.g., fartheraway from the ISM band). However, load unbalance may result by too manyUEs making the same handover request. In addition, some UEs mayarbitrary request handover based on reporting fake IDC problem. It isthus proposed that an UE triggers FDM solution based on accurate IDCinterference measurement result.

FIG. 6 illustrates one example of time division multiplexing (TDM)solution for IDC interference avoidance in wireless network 60. Wirelessnetwork 60 comprises an eNB61 and UE62-64 served by eNB61. In theexample of FIG. 6, UE62-64 may request certain LTE off duration (e.g.,depicted by slashed shade) for resource allocation to avoid IDCinterference. Because the timing requirement in each UE is independent(e.g., the requested LTE off durations may be the same from each UE), itis difficult for eNB61 to efficiently schedule and allocate radioresource. User throughput may also be degraded when TDM solution isactivated. It is thus proposed that an UE triggers TDM solution based onaccurate IDC interference measurement result.

FIG. 7 illustrates a method of triggering IDC interference mitigationsolution in wireless network 70 in accordance with one novel aspect.Wireless network 70 comprises an eNB71, a WiFi AP72, and an UE73. UE73comprises an LTE/WiMAX radio module (e.g., transceiver) 74, an ISMBT/WiFi radio module (e.g., transceiver) 75, and a control entity 76. Inone novel aspect, control entity 76 learns ISM Tx/Rx activity fromBT/WiFi transceiver 75 (step 1) and informs the ISM Tx/Rx timinginformation to LTE/WiMAX transceiver 74 (step 2). Based on the ISM Tx/Rxtiming information, LTE/WiMAX radio module 74 measures IDC interference(step 3) and triggers IDC interference avoidance mechanism if certainconditions are satisfied (step 4). In addition, LTE/WiMAX radio module74 reports ISM traffic and scheduling information to eNB71 to assist IDCconfiguration.

FIG. 8 is a simplified block diagram of a wireless device 81 having acentral control entity. Wireless device 81 comprises memory 84, aprocessor 85 having a central control entity 86, a LTE/LTE-A transceiver87, a WiFi transceiver 88, a Bluetooth transceiver 89, and bus 105. Inthe example of FIG. 8, central control entity 86 is a logical entityphysically implemented within processor 85, which is also used fordevice application processing for device 81. Alternatively, centralcontrol entity 86 is a logical entity implemented within a processorthat is physically located within the LTE/WiMAX transceiver, the WiFitransceiver, or the BT transceiver. Central control entity 86 isconnected to various transceivers within device 81, and communicateswith the various transceivers via bus 105. For example, WiFi transceiver88 transmits WiFi signal information and/or WiFi traffic and schedulinginformation to central control entity 86 (e.g., depicted by a dottedline 101). Based on the received WiFi information, central controlentity 86 informs WiFi Tx/Rx timing information to LTE/LTE-A transceiver87 (e.g., depicted by a dotted line 102). In one embodiment, the LTEradio module measures the received radio signal strength or quality andcalculates measurement result for IDC interference based on the WiFiTx/Rx timing information. If the measurement result satisfies a certaincondition, then the LTE radio module further communicates with itsserving base station eNB82 to trigger various coexistence interferencemitigation mechanisms (e.g., depicted by a dotted line 103).

There are many different interference mitigation mechanisms. Somemechanisms only require UE internal coordination, such as deactivate thetransmission of one radio module when the other co-located radio moduleis receiving desired radio signals. On the other hand, some mechanismsrequire network assistance, such as an UE sending an indication to abase station to trigger network-assisted solution. Via the indication,the UE may request changing its serving frequency to be farther awayfrom the frequency location of the coexistence ISM interference signal(e.g., FDM solution). Via the indication, the UE may also requestreserving certain time slots not to be scheduled for data transmissionor reception (e.g., TDM solution).

FIG. 9 illustrates one embodiment of triggering ISM radio activation ordeactivation based on measurement to cellular system. In the example ofFIG. 9, an LTE/WiMAX transceiver is co-located with a WiFi/BTtransceiver in a wireless device. The transmit (Tx) signal by theWiFi/BT transceiver (e.g., WiFi/BT Tx signal 91) is very close to thereceive (Rx) signal for the LTE/WiMAX transceiver (e.g., LTE/WiMAX RXsignal 92) in frequency domain. As a result, the out of band (OOB)emission and spurious emission by the WiFi/BT transceiver is relativelyhigh to the LTE/WiMAX transceiver resulted by imperfect TX filter and RFdesign. However, if the LTE/WiMAX Rx signal power is higher than certainlevel, then the IDC interference can be ignored even in worst case(e.g., with shortest frequency separation between LTE/WiMAX and WiFi/BT,under given filter performance). For example, as long as the LTE/WiMAXRx signal power is higher than the maximum coexistence interferencelevel that may possibly happen under the given filter performance andthe known frequency separation, the wireless device does not need todeactivate its ISM radio at all. The same concept can be used to triggerISM radio activation. For example, if the LTE/WiMAX Rx signal power ishigher than the aforementioned threshold, then the wireless device canfreely activate its ISM radio.

In general, the novel IDC triggering mechanism relies on radio signalmeasurement result and a corresponding condition (e.g., a thresholdvalue) to determine whether any IDC interference avoidance solutionneeds to be triggered. In another word, an IDC interference avoidancesolution is triggered only if the measurement result satisfies a certaincondition. Such IDC triggering mechanism prevents unnecessary andarbitrary IDC request from the UEs and thus improves network efficiency.The radio signal measurement to cellular system may include receivedsignal strength (e.g., RSRP in LTE, or RSSI in WiMAX), received signalquality (e.g., RSRQ in LTE, or CINR in WiMAX), received interferencepower level, or channel quality indicator (CQI). The triggeringcondition may be in the form of the original measurement such asRSRP/RSRQ, or CQI. The triggering condition may be further derived basedon the original measurement, such as in the form of effective throughput(e.g., a function of CQI), latency or block error rate (BLER) base onthe aforementioned measurement results. An LTE/WIMAX device can activateits ISM radios if the measurement result is better than a threshold. Onthe other hand, the LTE/WiMAX device needs to de-activate its ISM radioor activate addition IDC interference mitigation mechanism if themeasurement result is worse than the threshold.

The condition for triggering IDC is not necessarily a fixed condition,but configurable instead. For example, a threshold may be configured bythe base station and stored in the mobile stations. The configurationparameters can be carried by radio resource control (RRC) signaling,media access control (MAC) control element (CE), or capabilitynegotiation signaling in LTE systems. In another example, the thresholdmay be pre-defined and stored in the mobile stations. The base stationmay configure different thresholds for different scenarios. For example,different in-device ISM radios (e.g., WiFi or BT), different ISMoperation modes (e.g., WiFi AP mode, BT connection setup, paging,scanning), and different frequency separation from ISM radio signals maybe considered by the base station in determining the thresholds.Moreover, different conditions may be applied to activate different IDCinterference mitigation mechanisms under different scenarios. Forexample, a first condition may only trigger UE internal coordination,while a second condition may further trigger UE reporting to eNB fornetwork assistance. In addition, the derivation of theconditions/thresholds may be based on the worst-case deployment scenariosuch as the worst case of frequency separation (e.g., 40 MH between Band40 and ISM band), or the worst case of filter performance (e.g., filtersjust meet RF emission mask).

FIG. 10 illustrates another embodiment of triggering IDC interferencemitigation in wireless network 100 using different thresholds. Wirelessnetwork 100 comprises an eNB111, a WiFi AP112, and UE113-UE115. UE113and UE114 are not capable to mitigate IDC interference without networkassistance (referred to as coexistence-non-capable), while UE115 hasimplemented such capability (referred to as coexistence-capable). In theexample of FIG. 10, a threshold of the RSRP measurement of LTE radiosignal is applied for each UE to report to eNB111. In general, thethreshold for coexistence-capable UE115 can be lower than the thresholdfor coexistence-non-capable UE113 and UE114 because of the IDCinterference mitigation capability. The RSRP measurement of each UEvaries with the location of the UE. As depicted by curve 116 in FIG. 10,the RSRP gradually drops when the UE moves away from the serving eNB111.A higher threshold #1 is applied for coexistence-non-capable UE113 andUE114, while a lower threshold #2 is applied for coexistence-capableUE115. Because the RSRP measurement for UE113 is higher than threshold#1, UE113 will not report IDC interference information to eNB111. On theother hand, because the RSRP measurement for UE114 is lower thanthreshold #1, UE114 will report IDC interference information to eNB111and trigger coexistence interference mitigation mechanisms. For UE115,because the RSRP measurement is lower than threshold #1 but higher thanthreshold #2, UE115 will not report IDC interference information toeNB111 because UE115 is capable to mitigate some of the IDC interferencewithout network assistance. It is noted that although RSRP is used forillustration, CQI measurement is also applicable in the example of FIG.10.

Because the IDC triggering solution relies on IDC interferencemeasurement result, it is thus critical to be able to obtain accuratemeasurement result that efficiently detects coexistence interference.Device coordination capability is required to support accuratemeasurement result. From LTE/WiMAX perspective, the LTE/WiMAXtransceiver first needs to know (e.g., via an internal controller)whether other in-device transceiver(s) is transmitting or receivingwithin limited time latency. More specifically, the LTE/WiMAXtransceiver needs to know the time duration when the LTE/WIMAXtransceiver can measure the coexistence interference due to WiFi/BTtransmission, the time duration when LTE/WiMAX could receive withoutcoexistence interference from the WiFi/BT transceivers. Based on thatknowledge, the LTE/WiMAX transceiver can measure coexistenceinterference and evaluate which frequencies may or may not be seriouslyinterfered (e.g., unusable frequencies) for LTE/WiMAX RX. If coexistenceinterference is higher than a threshold, the LTE/WiMAX transceiver willthen indicate the unusable frequencies to the eNB based on themeasurement result for triggering IDC interference mitigation.

In LTE systems, reference signal received power (RSRP) and referencesignal received quality (RSRQ) are commonly measured by the UE torepresent radio signal strength, quality, and interference level. RSRPis defined as the linear-average over the power contributions of theresource elements that carry cell-specific reference signals withinconsidered measurement frequency bandwidth. The number of resourceelements within the considered measurement frequency bandwidth andwithin the measurement period that are used by the UE to determine RSRP,however, is left up to the UE implementation with the limitation thatcorresponding measurement accuracy requirements have to be fulfilled.

FIG. 11 illustrates an example of IDC interference measurement inaccordance with one novel aspect. The top half of FIG. 11 illustratesthat the UE normally samples the received reference signal power levelconsecutively (i.e., every five subframes (5 ms)) and take the averagewith certain weighting. However, interfering signals from WiFi/BT maynot be transmitted by the WiFi/BT radios when the UE is sampling for LTEmeasurement (e.g., due to bursty WiFi traffic). In addition, interferingsignal power level may be time variant (e.g., due to BT frequencyhopping). In the example of FIG. 11, for WiFi interfering signals, thereis no WiFi Tx activity at the first three sampling points. Similarly,for BT interfering signals, there is no BT Tx activity at the third andthe fourth sampling points, and there is only low BT Tx power at thefirst sampling point. If the UE uses all four sampling points and takesthe average in calculating the RSRP/RSRQ measurement result, suchRSRP/RSRQ measurement result will be very unreliable, and cannot detectcoexistence interference effectively.

The bottom half of FIG. 11 illustrates a novel mechanism of determiningthe RSRP/RSRQ measurement result based on the transmission activity ofthe in-device WiFi/BT radios. If the LTE/WiMAX radio knows the timinginformation of the WiFi/BT Tx activity, then the LTE/WiMAX radio can usethe timing information in calculating the RSRP/RSRQ measurement result.In the example of FIG. 11, the UE still measures the received referencesignal power level at four consecutive sampling points, but then skipscertain sampling points in calculating the measurement result. Forexample, if the co-located radio is WiFi, then the UE skips the firstthree sampling points (because they include no WiFi Tx power) incalculating the RSRP measurement result. If the co-located radio is BT,then the UE skips the first, the third, and the fourth sample points(because they include no or low BT TX power) in calculating the RSRPmeasurement result. Alternatively, the UE may even skip measuring theRSRP at those time instances when WiFi/BT radios are not transmittinginterfering signals. By skipping the sampling points formeasurement/calculation when there is no interfering signal, themeasurement result is more reliable in detecting coexistenceinterference.

Once the UE calculates that the measurement result (e.g., the RSRP orinterference level) is lower or higher than a configured thresholdvalue, then the UE triggers IDC interference mitigation mechanism. InLTE systems, most UE activities including DRX configuration and handoverprocedures are controlled by the network. Therefore, the UE reports IDCinterference indication to its serving eNB and in response the eNB helpsto trigger IDC interference mitigation mechanism. For example, the UEmay report to the eNB the frequency channels that are affected, orindicate to the eNB for handover operation. In one novel aspect, the UEalso transmits special ISM traffic pattern of the in-device WiFi/BTradios to its serving eNB, which triggers the eNB scheduler to configureDRX/DTX to avoid interference in time domain.

FIG. 12 illustrates an example of reporting traffic and schedulinginformation in wireless network 120 in accordance with one novel aspect.Wireless network 120 comprises a base station eNB121, a WiFi AP122, andan UE123. UE123 comprises an LTE/WiMAX transceiver 124, a WiFitransceiver 125, and a control entity 126. First, the control entityhelps the LTE/WiMAX transceiver to learn the WiFi traffic pattern (step1). Once UE123 determines to trigger IDC interference mitigationmechanism based on measurement result, LTE/WiMAX transceiver 124 reportsthe WiFi traffic pattern to eNB121 (step 2). Based on the WiFi trafficpattern, eNB121 is then able to schedule DRX/DTX configuration to avoidinterference (step 3). As illustrated in FIG. 12, eNB121 schedulesLTE/WiMAX UL Tx or Rx opportunity to avoid interference with WiFi beacontransmission in time domain. The scheduling may include onDurationTimer,drx-InactivityTimer, drx-RetransmissionTimer, longDRX-Cycle, the valueof the drxStartOffset, the drxShortCycleTimer, shortDRX-Cycle orstarting time. As a result, the WiFi beacons are protected from IDCinterference (step 4).

Typically, for WiFi traffic, the traffic pattern information may includeindication for WiFi beacon Tx/Rx time information, the periodicity,variation, and/or start time of a bursty traffic (e.g., every 100 mswith variation <1 ms, and start from 3 subframes after). For Bluetoothtraffic, the traffic pattern information may include operation mode(e.g., eSCO, A2DP), periodicity, and required Tx/Rx slot number. Theindication can also be an index that is associated with a pre-definedtraffic pattern. For example, index=0 is associated with WiFi beacon,index=1 is associated with eSCO, and index=2 is associated with A2DP.Such indication is suitable to support ISM radios with pre-definedtraffic patterns. Although the eNB may not always avoid collision, butit will schedule LTE traffic in best effort manner. From UE perspective,it may stop LTE Tx autonomously to avoid interference.

FIG. 13 is a flow chart of a method of triggering IDC interferencemitigation. In step 131, a first radio module of a wireless devicemeasures a received reference signal. The first radio module isco-located with a second radio module, and the measurement is based on aplurality of sampling instances. For example, the measurement isperformed every 5 ms consecutively. In step 132, the first radio moduleobtains one or more sampling instances, and during those samplinginstances, the second radio module is transmitting radio signals. Instep 133, the first radio module uses the obtained sampling instancesinformation to calculate radio signal measurement result. In step 134,the device triggers IDC interference mitigation mechanism if themeasurement result satisfies a certain condition. For example, the firstradio module reports interference information to a base station fornetwork-assisted interference mitigation solution. The condition may bea threshold value of the measurement result for the received radiosignal. The threshold is configurable when applied in differentscenarios.

FIG. 14 is a flow chart of a method of reporting traffic and schedulinginformation for IDC mitigation. In step 141, a first radio module of awireless device reports IDC interference information to a base stationbased on radio signal measurement result. In step 142, the first radiomodule obtains traffic and scheduling information of a second radiomodule that is co-located with the first radio module. In step 143, thefirst radio module reports the traffic and scheduling information to thebase station. In response to the reported traffic and schedulinginformation, the first radio module is scheduled by the base station fortransmitting and receiving radio signals over specific time duration orfrequency channels and thereby mitigating IDC interference.

Although the present invention has been described in connection withcertain specific embodiments for instructional purposes, the presentinvention is not limited thereto. For example, although an LTE-advancedor WiMAX mobile communication system is exemplified to describe thepresent invention, the present invention can be similarly applied toother mobile communication systems, such as Time Division SynchronousCode Division Multiple Access (TD-SCDMA) systems. Accordingly, variousmodifications, adaptations, and combinations of various features of thedescribed embodiments can be practiced without departing from the scopeof the invention as set forth in the claims.

What is claimed is:
 1. A method comprising: triggering an in-devicecoexistence (IDC) interference mitigation mechanism based on radiosignal measurement result by a first radio module if the measurementresult satisfies a first condition; obtaining traffic and schedulinginformation of a second radio module co-located with the first radiomodule; and reporting the traffic and scheduling information to a basestation from the first radio module if the measurement result satisfiesa second condition, wherein the first radio module receives informationfrom the base station for scheduling transmitting or receiving radiosignals over specific time duration or frequency channels based at leastin part on the reported traffic and scheduling information and therebymitigating IDC interference.
 2. The method of claim 1, wherein thesecond radio module is a WiFi module, and wherein the traffic andscheduling information comprises WiFi Beacon transmission timeinformation.
 3. The method of claim 1, wherein the second radio moduleis a Bluetooth module, and wherein the traffic and schedulinginformation comprises Bluetooth traffic pattern information.
 4. Themethod of claim 1, wherein the traffic and scheduling informationcomprises an index associated with a predefined traffic pattern.
 5. Themethod of claim 1, wherein the first condition is a higher referencesignal received power (RSRP) threshold, and wherein the second conditionis a lower RSRP threshold.
 6. A user equipment (UE) comprising: a firstradio module that triggers an in-device coexistence (IDC) interferencemitigation mechanism based on radio signal measurement result if themeasurement result satisfies a first condition; a central control entitythat obtains traffic and scheduling information of a second radio moduleco-located with the first radio module; and an antenna that transmitsthe traffic and scheduling information to a base station from the firstradio module if the measurement result satisfies a second condition,wherein the first radio module receives information from the basestation for scheduling transmitting or receiving radio signals overspecific time duration or frequency channels based at least in part onthe reported traffic and scheduling information and thereby mitigatingIDC interference.
 7. The UE of claim 6, wherein the second radio moduleis a WiFi module, and wherein the traffic and scheduling informationcomprises WiFi Beacon transmission time information.
 8. The UE of claim6, wherein the second radio module is a Bluetooth module, and whereinthe traffic and scheduling information comprises Bluetooth trafficpattern information.
 9. The UE of claim 6, wherein the traffic andscheduling information comprises an index associated with a predefinedtraffic pattern.
 10. The UE of claim 6, wherein the first condition is ahigher reference signal received power (RSRP) threshold, and wherein thesecond condition is a lower RSRP threshold.